U.S. patent application number 11/726734 was filed with the patent office on 2008-01-17 for carrier frequency shifting in mobile communications.
This patent application is currently assigned to Nokia Corporation. Invention is credited to Jari Hulkkonen, Kari Niemela, Olli Piirainen, Mikko Saily.
Application Number | 20080014877 11/726734 |
Document ID | / |
Family ID | 38609871 |
Filed Date | 2008-01-17 |
United States Patent
Application |
20080014877 |
Kind Code |
A1 |
Hulkkonen; Jari ; et
al. |
January 17, 2008 |
Carrier frequency shifting in mobile communications
Abstract
The specification and drawings present a new method, system,
apparatus and software product for carrier frequency shifting in
mobile communication systems, e.g., for eliminating or reducing
interference, e.g., for a communication between a mobile station
and a network element. The communication between the mobile station
and the network element may be performed within a GSM/EDGE radio
access network. A signal (e.g., a DSR or MDSR carrier) and at least
one further signal (e.g., a speech carrier) are identified, wherein
bandwidths of the signal and of the at least one further signal
overlap. Then, a frequency shift for said signal may be determined
according to a predetermined criterion and a carrier frequency of
the signal may be shifted by the determined frequency shift, e.g.,
for eliminating or reducing the interference.
Inventors: |
Hulkkonen; Jari; (Oulu,
FI) ; Niemela; Kari; (Oulu, FI) ; Piirainen;
Olli; (Oulu, FI) ; Saily; Mikko; (Sipoo,
FI) |
Correspondence
Address: |
WARE FRESSOLA VAN DER SLUYS & ADOLPHSON, LLP
BRADFORD GREEN, BUILDING 5
755 MAIN STREET, P O BOX 224
MONROE
CT
06468
US
|
Assignee: |
Nokia Corporation
|
Family ID: |
38609871 |
Appl. No.: |
11/726734 |
Filed: |
March 22, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60793396 |
Apr 19, 2006 |
|
|
|
Current U.S.
Class: |
455/114.2 |
Current CPC
Class: |
H04W 72/082
20130101 |
Class at
Publication: |
455/114.2 |
International
Class: |
H04B 1/02 20060101
H04B001/02 |
Claims
1. A method, comprising: identifying a signal and at least one
further signal in a service based mobile communication system,
wherein bandwidths in a frequency domain of the signal and of the
at least one further signal overlap; and determining a frequency
shift for shifting a carrier frequency of said signal according to
a predetermined criterion.
2. The method of claim 1, wherein said determining the frequency
shift for said signal according to the predetermined criterion is
performed using at least one of: a bandwidth of the signal, a
bandwidth of the at least one further signal, the carrier frequency
of the signal, and a degree of said overlap of said bandwidths.
3. The method of claim 1, wherein said determining the frequency
shift for said signal according to the predetermined criterion
comprises: identifying that said signal is interfering with said at
least one further signal according to a predetermined rule, and
selecting the frequency shifting, if said overlapping of said
bandwidths of said interfering signals is larger than a
pre-selected amount.
4. The method of claim 1, wherein said frequency shift is a fixed
offset.
5. The method of claim 1, wherein said signal has a dual symbol
rate of 13/24 MHz with said bandwidth at half power substantially
equals 541 kHz, said signal has a modified dual symbol rate of
13/32 MHz with said bandwidth at half power substantially equals
405 kHz, or said signal has a rate of 13/48 or 13/40 MHz with said
bandwidth at half power substantially equals 325 kHz.
6. The method of claim 1, wherein said frequency shift is at least
one of: plus or minus 200 kHz, and plus or minus 100 kHz.
7. The method of claim 1, wherein said signal and said at least one
further signal are for a communication between a mobile station and
a network element in said mobile communication system.
8. The method of claim 7, wherein said signal and said at least one
further signal are for an uplink communication from a mobile
station to a network element.
9. The method of claim 7, wherein said communication between the
mobile station and the network element is performed within an
evolved global system for mobile communications/enhanced data rates
for global evolution radio access network.
10. The method of claim 7, wherein said identifying or said
determining is performed by at least one of: the network element,
and the mobile station.
11. The method of claim 7, wherein said identifying and said
determining is performed by the network element and said signal is
received by said network element from the mobile station, and the
method further comprises: providing an instruction signal
comprising said frequency shift by said network element to said
mobile station for shifting the carrier frequency of said
signal.
12. The method of claim 7, wherein said identifying and said
determining is performed by the mobile station and said signal is
provided by the mobile station to the network element, and the
method further comprises: shifting by said mobile station a carrier
frequency of said signal by said frequency shift.
13. The method of claim 1, wherein said at least one further signal
is at least one out of: a speech signal, a data signal using an
enhanced general packet radio service, and a data signal using a
dual symbol rate or a modified dual symbol rate.
14. The method of claim 1, wherein said service based mobile
communication system is configured to be for at least one of the
following services: a dual symbol rate service, a modified symbol
rate service, and an enhanced general packet radio service.
15. The method of claim 1, wherein said shifting the carrier
frequency is for avoiding or minimizing overlapping of said
bandwidths.
16. A computer program product comprising: a computer readable
storage structure embodying computer program code thereon for
execution by a computer processor with said computer program code,
wherein said computer program code comprises instructions for
performing the method of claim 1, indicated as being performed by
any component or a combination of components of said mobile
communication system.
17. A method, comprising: generating an uplink signal by a mobile
station of a mobile communication system, wherein a carrier
frequency of said signal is shifted by a frequency shift; and
transmitting said signal by said mobile station to a network
element, wherein said signal and at least one further signal in
said mobile communication system are identified, wherein bandwidths
in a frequency domain of the signal and of the at least one further
signal overlap before shifting said carrier frequency of the signal
by the frequency shift, and said frequency shift is determined
using a predetermined criterion.
18. The method of claim 17, wherein said network element is a base
transceiver station, and the mobile station is a wireless
communication device, a portable device, a mobile communication
device, a mobile phone or a mobile camera phone.
19. A mobile communication system, comprising: a frequency shift
determining block configured to identify a signal and at least one
further signal in said mobile communication system, wherein
bandwidths in a frequency domain of the signal and of the at least
one further signal overlap, and further to determine a frequency
shift for said signal according to a predetermined criterion; a
signal generating block configured to shift a carrier frequency of
said signal by the frequency shift; a transmitter configured to
transmit said signal with the frequency shift; and a receiver
configured to receive said signal with the frequency shift.
20. The mobile communication system of claim 19, wherein a network
element of said mobile communication system comprises said
frequency shift determining block and said receiver, and a mobile
station of mobile communication system comprises said signal
generating block and the transmitter.
21. A mobile station of a mobile communication system, comprising:
an uplink scheduling and signal generating module configured to
generate an uplink signal, wherein a carrier frequency of said
signal is shifted by a frequency shift; and a module configured to
transmit said signal to a network element, wherein said signal and
at least one further signal in said mobile communication system are
identified, wherein bandwidths in a frequency domain of the signal
and of the at least one further signal overlap before shifting said
carrier frequency of the signal by the frequency shift, and said
frequency shift is determined using a predetermined criterion.
22. The mobile station of claim 21, wherein the uplink scheduling
and signal generating module is further configured to determine the
frequency shift for said signal according to the predetermined
criterion using at least one of: a bandwidth of the signal, a
bandwidth of the at least one further signal, the carrier frequency
of the signal, and a degree of said overlap of said bandwidths.
23. The mobile station of claim 21, wherein the uplink scheduling
and signal generating module is further configured to determine the
frequency shift for said signal according to the predetermined
criterion by: identifying that said signal is interfering with said
at least one further signal according to a predetermined rule, and
selecting the frequency shifting, if said overlapping of said
bandwidths of said interfering signals is larger than a
pre-selected amount.
24. The mobile station of claim 21, wherein said frequency shift is
a fixed offset.
25. The mobile station of claim 21, wherein said signal has a dual
symbol rate of 13/24 MHz with said bandwidth at half power
substantially equals 541 kHz, said signal has a modified dual
symbol rate of 13/32 MHz with said bandwidth at half power
substantially equals 405 kHz, or said signal has a rate of 13/48 or
13/40 MHz with said bandwidth at half power substantially equals
325 kHz.
26. The mobile station of claim 21, wherein said frequency shift is
at least one of: plus or minus 200 kHz, and plus or minus 100
kHz.
27. The mobile station of claim 21, wherein said at least one
further signal is at least one out of: a speech signal, a data
signal using an enhanced general packet radio service, and a data
signal using a dual symbol rate or a modified dual symbol rate.
28. A network element of a mobile communication system, comprising:
a frequency shift determining and scheduling block configured to
identify a signal and at least one further signal in said mobile
communication system, wherein bandwidths in a frequency domain of
the signal and of the at least one further signal overlap, and
further configured to determine a frequency shift of the signal
using a predetermined criterion, and still further configured to
provide an instruction to a mobile station to shift a carrier
frequency of said signal by the frequency shift; and a receiver
configured to receive said signal with the frequency shift from the
mobile station.
29. The network element of claim 28, wherein the frequency shift
determining and scheduling block is configured to determine the
frequency shift for said signal according to the predetermined
criterion using at least one of: a bandwidth of the signal, a
bandwidth of the at least one further signal, the carrier frequency
of the signal, and a degree of said overlap of said bandwidths.
30. The network element of claim 28, wherein the frequency shift
determining and scheduling block is configured to determine the
frequency shift for said signal according to the predetermined
criterion by: identifying that said signal is interfering with said
at least one further signal according to a predetermined rule, and
selecting the frequency shifting, if said overlapping of said
bandwidths of said interfering signals is larger than a
pre-selected amount.
31. The network element of claim 28, wherein said signal has a dual
symbol rate of 13/24 MHz with said bandwidth at half power
substantially equals 541 kHz, said signal has a modified dual
symbol rate of 13/32 MHz with said bandwidth at half power
substantially equals 405 kHz, or said signal has a rate of 13/48 or
13/40 MHz with said bandwidth at half power substantially equals
325 kHz.
32. The network element of claim 28, wherein said frequency shift
is at least one of: plus or minus 200 kHz, and plus or minus 100
kHz.
33. The network element of claim 28, wherein said at least one
further signal is at least one out of: a speech signal, a data
signal using an enhanced general packet radio service, and a data
signal using a dual symbol rate or a modified dual symbol rate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Patent
Application Ser. No. 60/793,396, filed on Apr. 19, 2006.
TECHNICAL FIELD
[0002] This invention generally relates to mobile communications
and more specifically to carrier frequency shifting in mobile
communication systems, e.g., for eliminating or reducing
interference.
BACKGROUND ART
[0003] Further evolution of EDGE (enhanced data rates for global
evolution) continues in 3GPP(3d generation partnership project)
Release 7 known as Evolved GERAN (GSM (global system for mobile
communications)/EDGE) radio access network) 3GPP. Dual Symbol Rate
(DSR) for uplink performance improvement is proposed as shown in
3GPP contributions, e.g., in GP-05261, Agenda Item 7.1.5.5,
"Updates for Dual Symbol Rate Section of the Feasibility Study on
Future GERAN Evolution", 3GPP TSG GERAN#27, Atlanta, USA. In the
DSR, the symbol rate of the GSM/EDGE is doubled and the transmitter
signal is allowed to overlap adjacent carriers. The DSR nearly
doubles UL (uplink) data spectral efficiency and is, therefore, the
interesting UL capacity enhancement feature for the EDGE evolution.
From the system performance point of view, frequency planning needs
to be considered carefully because adjacent DSR carriers are
partially overlapping, which brakes the basic frequency planning
that is made for the normal 200 kHz carriers because the DSR
carriers have a spectrum of approximately 600 kHz wide (a 3 dB
bandwidth of 541 kHz) compared to the normal 200 kHz wide carriers
as shown in FIG. 1. In the DSR concept the symbol rate was doubled,
thus doubling the bit rate over the air interface can be obtained
with the same modulation. This makes it possible to use the current
EGPRS (enhanced general packet radio service) coding schemes for
the DSR, only transmit them with the double bit rate.
[0004] Also in the case of EGPRS, interference conditions need to
be considered when data connections are allocated to the hopping
layer. Data connections are typically causing more interference
than speech connections (e.g., because data uses higher transmitter
powers since C/I (carrier-to-interference ratio) and the target is
higher compared to AMR/FS (adaptive multi-rate full rate
speech).
[0005] As shown in FIG. 1, the DSR carrier overlaps with adjacent
carriers so that the interference situation is worse in the network
using DSR; then the original frequency reuse is blurred in the DSR
case. As adjacent DSR carriers are overlapping, usage of DSR makes
the interference situation uncontrolled when basic frequency
planning is used.
[0006] Moreover, in the case of the EGPRS, increased interference
from data connections can be a problem, data traffic is allocated
to hopping layer which was originally planned for the speech
traffic only. Increased interference decreases speech traffic
performance.
[0007] In the GSM system, co-channel and adjacent channel
interference is controlled with the frequency planning. Data and
speech traffic can be separated for different frequencies so that
speech and data are not interfering with each other. Data traffic
can be allocated to BCCH (broadcast control channel) frequencies as
far as there are enough resources in a BCCH TRX (transceiver). But,
when the BCCH TRX capacity is not enough for the data transmission,
a certain amount of hopping layer resources need to be reserved for
data. In that case, speech and data connections are interfering
with each other. The EGPRS power control is one way to control the
interference caused by the data traffic, but then the trade-off
between the data throughput and the speech quality is made.
[0008] For the DSR concept proposed for the EDGE evolution in 3GPP
there are no specific solutions available to control interference
caused by wider DSR carriers. As stated in the DSR feasibility
study (see GP-052610 quoted above), the current solution is to use
IRC (interference rejection combining) receivers and try to cope
with increased interference in the network. Also, advanced channel
allocation methods which allocate channels based on interference
conditions could be used, like proposed in the invention "Radio
channel allocation and link adaptation in cellular
telecommunication system" by Jari Hulkkonen and Olli Piirainen,
filed as a Finnish patent application No. 20055687 on Dec. 21,
2005, but those require more complex allocation algorithms,
interference evaluation, etc.
[0009] A new uplink (UL) concept, called Modified DSR (MDSR), is
described and claimed in co-pending, co-owned application (Att.
Doc. No 944-008.036) filed on even date herewith. The modified dual
symbol rate (MDSR ) can be one and a half times a symbol rate of an
uplink speech service, e.g., the current GSM/EDGE symbol rate (
13/48 MHz) in the mobile communication system, thus the modified
dual symbol rate is substantially 13/32 MHz with a 3 dB (half
power) bandwidth of about 405 kHz. The uplink signal with the MDSR
may be modulated using a quadrature amplitude modulation (QAM),
e.g., 16-QAM with 16 states and optionally a quadrature phase-shift
keying (QPSK, or .pi./4-QPSK) modulation.
[0010] Moreover, the uplink signal utilizing the MDSR may be
modulated using the quadrature amplitude modulation (e.g., 16-QAM)
having a bit rate substantially equal to two times of a peak bit
rate of the uplink EGPRS service, i.e., having the same peak bit
rate as provided in case of the DSR. Variable coding rates may be
provided by several MCSs (modulation and coding schemes).
[0011] Furthermore, the uplink signal utilizing the MDSR may be
optionally modulated using the quadrature phase-shift keying (QPSK)
modulation having a peak bit rate substantially equal to the bit
rate of the uplink EGPRS service.
[0012] Both DSR and MDSR carriers overlap with adjacent carriers.
DSR carrier overlapping with EDGE carriers is shown in FIG. 1. Note
that even though MDSR spectrum is only about 400 kHz, it still can
overlap with 3 carriers. DSR/MDSR carrier overlapping can blur
original GSM/EDGE frequency planning and can make an interference
situation uncontrolled. This degrades the system performance
especially for legacy (non DSR or MDSR) services, e.g. circuit
switched speech.
[0013] Moreover, the DSR and MDSR may need a wider channel filter
than exists in a typical BSS (base station subsystem) and also it
may not be possible to tune receiving frequencies out of normal 200
kHz channel raster. Also, by using separate frequency bands
(including a guard band), a DSR/MDSR interference can be isolated
from the legacy services. However, spectrum splitting requires
large bandwidth and wastes resources.
DISCLOSURE OF THE INVENTION
[0014] According to a first aspect of the invention, a method,
comprises: identifying a signal and at least one further signal in
a service based mobile communication system, wherein bandwidths in
a frequency domain of the signal and of the at least one further
signal overlap; and determining a frequency shift for shifting a
carrier frequency of the signal according to a predetermined
criterion.
[0015] According further to the first aspect of the invention, the
determining the frequency shift for the signal according to the
predetermined criterion may be performed using at least one of: a
bandwidth of the signal, a bandwidth of the at least one further
signal, the carrier frequency of the signal, and a degree of the
overlap of the bandwidths.
[0016] Further according to the first aspect of the invention, the
determining the frequency shift for the signal according to the
predetermined criterion may comprise: identifying that the signal
is interfering with the at least one further signal according to a
predetermined rule, and selecting the frequency shifting, if the
overlapping of the bandwidths of the interfering signals is larger
than a pre-selected amount.
[0017] Still further according to the first aspect of the
invention, the frequency shift may be a fixed offset.
[0018] According yet further to the first aspect of the invention,
the signal may have a dual symbol rate of 13/24 MHz with the
bandwidth at half power substantially equals 541 kHz, the signal
may have a modified dual symbol rate of 13/32 MHz with the
bandwidth at half power substantially equals 405 kHz, or the signal
may have a rate of 13/48 or 13/40 MHz with the bandwidth at half
power substantially equals 325 kHz.
[0019] According still further to the first aspect of the
invention, the frequency shift may be at least one of: plus or
minus 200 kHz, and plus or minus 100 kHz.
[0020] According further still to the first aspect of the
invention, the signal and the at least one further signal may be
for a communication between a mobile station and a network element
in the mobile communication system. Further, the signal and the at
least one further signal may be for an uplink communication from a
mobile station to a network element. Still further, the
communication between the mobile station and the network element
may be performed within an evolved global system for mobile
communications/enhanced data rates for global evolution radio
access network. Yet still further, the identifying or the
determining may be performed by at least one of: the network
element, and the mobile station. Still yet further, the identifying
and the determining may be performed by the network element and the
signal may be received by the network element from the mobile
station, and the method may further comprise: providing an
instruction signal comprising the frequency shift by the network
element to the mobile station for shifting the carrier frequency of
the signal. Yet further still, the identifying and the determining
may be performed by the mobile station and the signal may be
provided by the mobile station to the network element, and the
method may further comprise: shifting by the mobile station a
carrier frequency of the signal by the frequency shift.
[0021] According yet further still to the first aspect of the
invention, the at least one further signal may be at least one out
of: a speech signal, a data signal using an enhanced general packet
radio service, and a data signal using a dual symbol rate or a
modified dual symbol rate.
[0022] Yet still further according to the first aspect of the
invention, the service based mobile communication system may be
configured to be for at least one of the following services: a dual
symbol rate service, a modified symbol rate service, and an
enhanced general packet radio service.
[0023] Still yet further according to the first aspect of the
invention, the shifting the carrier frequency may be for avoiding
or minimizing overlapping of the bandwidths.
[0024] According to a second aspect of the invention, a computer
program product comprises: a computer readable storage structure
embodying computer program code thereon for execution by a computer
processor with the computer program code, wherein the computer
program code comprises instructions for performing the first aspect
of the invention, indicated as being performed by any component or
a combination of components of the mobile communication system.
[0025] According to a third aspect of the invention, a method,
comprises: generating an uplink signal by a mobile station of a
mobile communication system, wherein a carrier frequency of the
signal is shifted by a frequency shift; and transmitting the signal
by the mobile station to a network element, wherein the signal and
at least one further signal in the mobile communication system are
identified, wherein bandwidths in a frequency domain of the signal
and of the at least one further signal overlap before shifting said
carrier frequency of the signal by the frequency shift, and the
frequency shift is determined using a predetermined criterion.
[0026] Still yet further according to the third aspect of the
invention, the network element may be a base transceiver station,
and the mobile station may be a wireless communication device, a
portable device, a mobile communication device, a mobile phone or a
mobile camera phone.
[0027] According to a fourth aspect of the invention, a mobile
communication system, comprises: a frequency shift determining
block configured to identify a signal and at least one further
signal in the mobile communication system, wherein bandwidths in a
frequency domain of the signal and of the at least one further
signal overlap, and further to determine a frequency shift for the
signal according to a predetermined criterion; a signal generating
block configured to shift a carrier frequency of the signal by the
frequency shift; a transmitter configured to transmit the signal
with the frequency shift; and a receiver configured to receive the
signal with the frequency shift.
[0028] According further to the fourth aspect of the invention, a
network element of the mobile communication system may comprise the
frequency shift determining block and the receiver, and a mobile
station of mobile communication system may comprise the signal
generating block and the transmitter.
[0029] According to a fifth aspect of the invention, a mobile
station of a mobile communication system, comprises: an uplink
scheduling and signal generating module configured to generate an
uplink signal, wherein a carrier frequency of the signal is shifted
by a frequency shift; and a module configured to transmit the
signal to a network element, wherein the signal and at least one
further signal in the mobile communication system are identified,
wherein bandwidths in a frequency domain of the signal and of the
at least one further signal overlap before shifting said carrier
frequency of the signal by the frequency shift, and the frequency
shift is determined using a predetermined criterion.
[0030] According further to the fifth aspect of the invention, the
uplink scheduling and signal generating module may be further
configured to determine the frequency shift for the signal
according to the predetermined criterion using at least one of: a
bandwidth of the signal, a bandwidth of the at least one further
signal, the carrier frequency of the signal, and a degree of the
overlap of the bandwidths.
[0031] Further according to the fifth aspect of the invention, the
uplink scheduling and signal generating module may be further
configured to determine the frequency shift for the signal
according to the predetermined criterion by: identifying that the
signal is interfering with the at least one further signal
according to a predetermined rule, and selecting the frequency
shifting, if the overlapping of the bandwidths of the interfering
signals is larger than a pre-selected amount.
[0032] Still further according to the fifth aspect of the
invention, the frequency shift may be a fixed offset.
[0033] According further to the fifth aspect of the invention, the
signal may have a dual symbol rate of 13/24 MHz with the bandwidth
at half power substantially equals 541 kHz, the signal may have a
modified dual symbol rate of 13/32 MHz with the bandwidth at half
power substantially equals 405 kHz, or the signal may have a rate
of 13/48 or 13/40 MHz with the bandwidth at half power
substantially equals 325 kHz.
[0034] According still further to the fifth aspect of the
invention, the frequency shift may be at least one of: plus or
minus 200 kHz, and plus or minus 100 kHz.
[0035] According further still to fifth aspect of the invention,
the at least one further signal may be at least one out of: a
speech signal, a data signal using an enhanced general packet radio
service, and a data signal using a dual symbol rate or a modified
dual symbol rate.
[0036] According to a sixth aspect of the invention, a network
element of a mobile communication system, comprises: a frequency
shift determining and scheduling block configured to identify a
signal and at least one further signal in the mobile communication
system, wherein bandwidths in a frequency domain of the signal and
of the at least one further signal overlap, and further configured
to determine a frequency shift of the signal using a predetermined
criterion, and still further configured to provide an instruction
to a mobile station to shift a carrier frequency of the signal by
the frequency shift; and a receiver configured to receive the
signal with the frequency shift from the mobile station.
[0037] According further to the sixth aspect of the invention, the
frequency shift determining and scheduling block may be configured
to determine the frequency shift for the signal according to the
predetermined criterion using at least one of: a bandwidth of the
signal, a bandwidth of the at least one further signal, the carrier
frequency of the signal, and a degree of the overlap of the
bandwidths.
[0038] Further according to the sixth aspect of the invention, the
frequency shift determining and scheduling block may be configured
to determine the frequency shift for the signal according to the
predetermined criterion by: identifying that the signal is
interfering with the at least one further signal according to a
predetermined rule, and selecting the frequency shifting, if the
overlapping of the bandwidths of the interfering signals is larger
than a pre-selected amount.
[0039] Still further according to the sixth aspect of the
invention, the signal may have a dual symbol rate of 13/24 MHz with
the bandwidth at half power substantially equals 541 kHz, the
signal may have a modified dual symbol rate of 13/32 MHz with the
bandwidth at half power substantially equals 405 kHz, or the signal
may have a rate of 13/48 or 13/40 MHz with the bandwidth at half
power substantially equals 325 kHz.
[0040] According further to the sixth aspect of the invention, the
frequency shift may be at least one of: plus or minus 200 kHz, and
plus or minus 100 kHz.
[0041] According still further to the sixth aspect of the
invention, the at least one further signal may be at least one out
of: a speech signal, a data signal using an enhanced general packet
radio service, and a data signal using a dual symbol rate or a
modified dual symbol rate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] For a better understanding of the nature and objects of the
present invention, reference is made to the following detailed
description taken in conjunction with the following drawings, in
which:
[0043] FIG. 1 is a schematic representation of a spectrum of dual
symbol rate (DSR) compared to basic GSM/EDGE spectrum;
[0044] FIGS. 2a through 2c are schematic representations
demonstrating DSR carrier frequency shifting with a 1/3 frequency
reuse for 12 carrier frequencies: a) carrier frequencies before a
DSR frequency shift; b) carrier frequencies after the DSR frequency
shift; and c) interfering cells for a 1/3 frequency reuse of 12
frequencies and 4 transceivers per cell, according to an embodiment
of the present invention;
[0045] FIGS. 3a through 3c are schematic representations
demonstrating MDSR carrier frequency shifting with a 1/3 frequency
reuse for 12 carrier frequencies: a) carrier frequencies before an
MDSR frequency shift; b) carrier frequencies after the MDSR
frequency shift (+100 kHz); and c) interfering cells for a 1/3
frequency reuse of 12 frequencies and 4 transceivers per cell,
according to an embodiment of the present invention;
[0046] FIGS. 4a through 4c are further schematic representations
demonstrating MDSR carrier frequency shifting with a 1/3 frequency
reuse for 12 carrier frequencies: a) carrier frequencies before an
MDSR frequency shift; b) carrier frequencies after the MDSR
frequency shift (+100 kHz); and c) interfering cells for a 1/3
frequency reuse of 12 frequencies and 4 transceivers per cell,
according to an embodiment of the present invention;
[0047] FIG. 5 is a block diagram of a mobile communication system
with carrier frequency shifting for eliminating or reducing
interference, according to an embodiment of the present
invention;
[0048] FIG. 6 is a flow chart for implementing carrier frequency
shifting in a mobile communication system, according to an
embodiment of the present invention.
[0049] FIG. 7 is a flow chart for implementing carrier frequency
shifting in a mobile communication system for eliminating or
reducing interference, according to an embodiment of the present
invention.
MODES FOR CARRYING OUT THE INVENTION
[0050] A new method, system, apparatus and software product are
presented for carrier frequency shifting in mobile communication
systems, e.g., for eliminating or reducing interference, e.g., for
a communication between a mobile station and a network element. The
communication between the mobile station (MS) and the network
element may be performed within an evolved global system for mobile
communications/enhanced data rates for global evolution (GSM/EDGE)
radio access network. The network element may be, e.g., a base
transceiver station (BTS). The mobile station may be (but is not
limited to): a mobile phone, a wireless device, a mobile camera
phone, etc. The frequency shifting can be applied to the signals in
an uplink (UP) direction (e.g., from the mobile station to the
network element) as well as in a downlink (DL) direction.
[0051] According to an embodiment of the present invention, a
signal (e.g., a DSR or MDSR packet switched data carrier) and at
least one further signal (e.g., a circuit switch speech carrier, a
data signal using EGPRS, and/or another DSR or MDSR carrier) in the
mobile communication system are identified, wherein bandwidths in a
frequency domain of the signal and of the at least one further
signal overlap. Then, a frequency shift for said signal may be
determined according to a predetermined criterion, and a carrier
frequency of the signal may be shifted by the determined frequency
shift. The determining the frequency shift according to the
predetermined criterion may be performed using at least one of the
following parameters: a bandwidth of the signal, a bandwidth of the
at least one further signal, the carrier frequency of the signal, a
degree of the bandwidth overlap. It is further noted that the
signal described herein can also have various symbol rates
including rates different than in the EGPRS (having symbol rate of
13/48 MHz with the bandwidth at half power substantially equals 180
kHz) such as a dual symbol rate of 13/24 MHz with the bandwidth at
half power substantially equals 541 kHz, a modified dual symbol
rate of 13/32 MHz with the bandwidth at half power substantially
equals 405 kHz, a symbol rate of 13/48 or 13/40 MHz with the
bandwidth at half power substantially equals 325 kHz for a Higher
Uplink performance for GERAN Evolution (HUGE), etc.
[0052] Moreover, the determining the frequency shift for the signal
according to the predetermined criterion may comprise of: a)
identifying that the signal interfering with the at least one
further signal according to a predetermined rule, and b) selecting
the frequency shifting, if the overlapping of the bandwidths of
said interfering signals is larger than a pre-selected amount for
eliminating or reducing the interference. The predetermined rule
can be, for example, overlapping in excess of a pre-selected
amount, e.g., of 100 kHz, 50%, etc. Then if the overlapping of said
bandwidths is larger than the pre-selected amount, the carrier
frequency of the signal is shifted by a frequency shift using a
predetermined criterion for eliminating or reducing the
interference. The frequency shift can be implemented "statically"
(wherein the frequency shift, e.g., is a fixed offset), i.e., for a
duration of a communication session such as a phone conversation or
transmission of an SMS (short message service) message or duration
of an uplink TBF (temporary block flow), or dynamically, i.e.,
changing the frequency shift during the communication session based
on the interference conditions.
[0053] FIGS. 2a through 2c show an example among others of
schematic representations demonstrating DSR (dual symbol rate)
carrier frequency shifting with a 1/3 frequency reuse for 12
carrier frequencies, wherein FIG. 2a shows carrier frequencies
before the DSR frequency shift, FIG. 2b shows carrier frequencies
after the DSR frequency shift; and FIG. 2c shows interfering cells
for the 1/3 frequency reuse of 12 frequencies and 4 transceivers
per cell, according to an embodiment of the present invention.
Numbers 0, 2 . . . , and 11 in FIGS. 2a-2c indicate frequencies
identifications (IDs) of 12 frequencies. Frequencies 3, 4 and 5 are
DSR frequencies and the rest of the frequencies (0-2, 6-11) are
speech carrier frequencies.
[0054] FIG. 2a shows that the DSR carrier frequencies (or DSR
carriers) 3 and 5 overlap with frequencies 2 and 6 that are used
for speech. However, when the DSR carrier 3 is shifted by +200 kHz
and the DSR carrier 5 is shifted by -200 kHz, as shown in FIG. 2b,
then all DSR carriers are fully overlapping, but there is no
overlapping the DSR carriers to the speech service (and vice
versa). Thus, interference between the DSR and legacy services can
be totally avoided between the adjacent sectors. From the DSR
performance point of view, there is no significant difference if
the interferer is located .+-.200 kHz from or exactly in the same
frequency, because DSR carriers separated with .+-.200 kHz are
still overlapping more than 50%, i.e., the frequency reuse between
DSR carriers is one in any case (from the interference point of
view).
[0055] FIGS. 3a through 3c show an example among others of
schematic representations demonstrating MDSR (modified dual symbol
rate) carrier frequency shifting with the 1/3 frequency reuse for
12 carrier frequencies, wherein FIG. 2a shows carrier frequencies
before the MDSR frequency shift, FIG. 2b shows carrier frequencies
after the MDSR frequency shift; and FIG. 2c shows interfering cells
for the 1/3 frequency reuse of 12 frequencies and 4 transceivers
per cell, according to a further embodiment of the present
invention. Numbers 0, 2 . . . , and 11 in FIGS. 3a-3c indicate
frequencies identifications (IDs) of 12 frequencies. Frequencies 3,
4 and 5 are MDSR frequencies and the rest of the frequencies (0-2,
6-11) are speech carrier frequencies.
[0056] FIG. 3a shows that the MDSR carrier frequencies (or MDSR
carriers) 3 and 5 overlap with frequencies 2 and 6, respectively,
that are used for speech. However, when each of the MDSR carriers
3, 4 and 5 is shifted by a fixed offset +100 kHz (alternatively the
MDSR carrier 4 can be shifted by -100 kHz) as shown in FIG. 3b,
then the MDSR carriers 3 and 4 are not overlapping with the speech
service (and vice versa) and only the MDSR carrier 5 still overlaps
with the speech carrier 6. Also the MDSR carriers 3 and 5 do not
overlap with each other and the MDSR carriers 4 insignificantly
overlaps with the MDSR carriers 3 and 5 such that the frequency
reuse may be still possibly used with carriers 3, 4 and 5. Thus,
interference between the DSR and legacy services can be
significantly reduced between the adjacent sectors.
[0057] FIGS. 4a-4c are similar examples of the MDSR frequency
shifting as shown in FIGS. 3a-3c, with the only difference that the
carrier 5 in FIG. 4b is shifted by -100 kHz, thus there is no
overlapping between the MDSR carrier 5 and the speech carrier 6 and
therefore no overlapping between the MDSR and speech carriers (and
vice versa).
[0058] In case of the MDSR frequency shifting of .+-.100 kHz, the
effect of reducing or eliminating interference may be even more
effective than the DSR frequency shifting as shown in FIG. 2b,
because in the MDSR case the number of overlapping carriers
decreases to 2, as shown in FIG. 3b (e.g., overlapping carriers 5
and 6) and in FIG. 4b (e.g., overlapping carriers 4 and 5).
[0059] Moreover, in case of the MDSR frequency shifting, it can be
chosen whether the carrier is shifted -100 or +100 kHz. This
selection of the appropriate frequency shift can be done based on
mobile station and/or network measurements. For example, if a
mobile station configured for providing the MDSR service receives a
strong BCCH signal from a neighboring cell, it potentially
interferes with that cell in the uplink. Therefore, based on the
frequency planning parameters, the frequency shifting can be done
so that the interference towards the potentially highly interfered
cell is avoided or significantly reduced. It is noted that examples
presented in FIGS. 2a-2c, 3a-3c and 4a-4c for the frequency reuse
of 1/3 are also applicable for other frequency reuse values and/or
time reuse, especially in case of 3-sectorized base stations.
[0060] A performance of the frequency shifting has been studied
with system and link simulations. Traffic model was mixed: packet
data traffic 20% and AMR (adaptive multi rate) speech traffic 80%.
The MDSR was used first without carrier frequency shifting and then
with fixed +100 kHz offset. The AMR speech service performance was
measured and it was noted that performance was clearly improved.
Number of bad AMR speech quality calls was 1.3% without the
frequency shift (offset) and 1.05% with the fixed +100 kHz offset.
Then, MDSR results show at least one dB gain for the MDSR data
performance for +100 kHz offset. It is expected that by selecting
plus or minus 100 kHz offset based on the interference conditions
(using, e.g., network plan and/or MS measurements) would further
improve the system performance.
[0061] FIG. 5 is an example among others of a block diagram of a
mobile communication system 10 with the carrier frequency shifting
(e.g., using DSR or MDSR signals) for eliminating or reducing
interference, according to an embodiment of the present invention;
and
[0062] In the example of FIG. 5, the mobile station (or user
equipment) 42 comprises an uplink scheduling and signal generating
module 46 and a transmitter/receiver/processing module 44. In the
context of the present invention, the mobile station 42 can be a
wireless communication device, a portable device, a mobile
communication device, a mobile phone, a mobile camera phone, etc.
In the example of FIG. 5, a network element 40 (e.g., a BTS or a
Node B) can comprise a transmitter 48, a frequency shift
determining and scheduling module 50 and a receiver 47. It is noted
that the module 46 can generally be means for signal generation or
a structural equivalence (or equivalent structure) thereof. Also,
the module 44 can generally be transmitting and/or receiving means,
e.g., a transceiver, or a structural equivalence (or equivalent
structure) thereof. Moreover, the receiver 47 can generally be
means for receiving the uplink signal, e.g., a transceiver, or a
structural equivalence (or equivalent structure) thereof.
Furthermore, the module 50 can generally be means for identifying
signals and for determining frequency shifts, or a structural
equivalence (or equivalent structure) thereof.
[0063] According to an embodiment of the present invention, the
network, e.g., the module 50 of the network element 50 (or it can
be another network element), may provide a frequency shift
instructions (i.e., signal 52). In case of the downlink (DL), these
instructions may be provided to the module 48 which will generate
and send a DL signal 56 (e.g., comprising data and/or voice
information) with the appropriate frequency shift to the mobile
station 42. The uplink (UL) frequency shift instructions (e.g., for
the DSR and/or MDSR frequency carriers) contained in the signal 52
are forwarded (signal 52a) to the module 44 of the mobile station
42 and then further forwarded (signal 52b) to the module 46. The
module 46 can use the uplink frequency shift instructions contained
in the signal 52b for generating an UL signal 54 (e.g., comprising
data and/or voice information), which is forwarded by the module 44
(signal 54a) to the receiver 47 of the network element 40.
Alternatively, the module 46 (instead or in addition to the module
50) can be used for determining the frequency shift according to
the predetermined criterion. The determination whether the
frequency shift is needed based on the interference conditions may
be performed by the module 50 consequently providing the
instruction signal 52 to the mobile station 42. Alternatively or in
addition, this determination whether the frequency shift is needed
for the uplink may be performed by the mobile station 42 (e.g., by
the module 46) based on the interference signals received by the
mobile station 42 from the neighboring cells.
[0064] According to an embodiment of the present invention, the
module 44, 46, 47, 48 or 50 can be implemented as a software block,
a hardware block or a combination thereof. Furthermore, each of the
modules 44, 46, 47, 48 or 50 can be implemented as a separate
module or can be combined with any other standard block of the
mobile station 42 or the network element 40, or it can be split
into several blocks according to their functionality. The
transmitter/receiver/processing block 44 can be implemented in a
plurality of ways and typically can include a transmitter, a
receiver, a CPU (central processing unit), etc. The transmitter and
receiver can be combined, for example, in one module such as
transceiver, as known in the art. The module 44 provides an
effective communication of the module 46 with the network element
40.
[0065] FIG. 6 is a flow chart for implementing carrier frequency
shifting in a mobile communication system for eliminating or
reducing interference, according to an embodiment of the present
invention.
[0066] The flow chart of FIG. 6 only represents one possible
scenario among others. The order of steps shown in FIG. 6 is not
absolutely required, so generally, the various steps can be
performed out of order. In a method according to the first
embodiment of the present invention, in a first step 57, a signal
(e.g., with DSR or MDSR) and at least one further signal are
identified by the network (e.g., a network element such as BTS, BSS
or Node B, etc.) and/or by the mobile station, wherein the
bandwidths in a frequency domain of the signal and of the at least
one further signal overlap.
[0067] In a next step 58, a frequency shift for that signal is
determined according to a predetermined criterion (e.g., using
bandwidths, carrier frequency, interference conditions, etc.) and
in a next step 59, the carrier frequency of the signal is shifted
by a frequency shift, e.g., for eliminating or reducing the
interference.
[0068] FIG. 7 is a flow chart for implementing carrier frequency
shifting in a mobile communication system specifically for
dynamically eliminating or reducing interference, according to an
embodiment of the present invention.
[0069] The flow chart of FIG. 7 only represents one possible
scenario among others. The order of steps shown in FIG. 7 is not
absolutely required, so generally, the various steps can be
performed out of order. In a method according to the first
embodiment of the present invention, in a first step 60, a signal
(e.g., with DSR or MDSR) interfering according to a predetermined
rule with at least one further signal is identified by the network
(e.g., a network element such as BTS, BSS or Node B, etc.) and/or
by the mobile station, wherein the bandwidths in a frequency domain
of the signal and of the at least one further signal overlap.
[0070] In a next step 62, it is ascertained whether the bandwidth
overlapping is larger than a predetermined amount. If that is not
the case, the process goes back to the step 60 to continue the
process of identification of the interference. However, if it is
determined that the bandwidth overlapping is larger than the
predetermined amount, in a next step 64, the carrier frequency of
the signal is shifted by a frequency shift using a predetermined
criterion for eliminating or reducing the interference.
[0071] It is further noted that, according to an embodiment of the
present invention, signalling of single frequency offset for the
DSR or MDSR (e.g., see signal 52a in FIG. 5) may be implemented in
a straightforward fashion, e.g., by one bit among frequency
parameters, but if that needs to be done dynamically or based on
the actual frequency, other methods may be applied, for example
using a bit map or a frequency list. Furthermore, in case of
multi-slot configurations, the mobile station may need to hop
between time slots to have or not have the frequency offset.
[0072] As explained above, the invention provides both a method and
corresponding equipment consisting of various modules providing the
functionality for performing the steps of the method. The modules
may be implemented as hardware, or may be implemented as software
or firmware for execution by a computer processor. In particular,
in the case of firmware or software, the invention can be provided
as a computer program product including a computer readable storage
structure embodying computer program code (i.e., the software or
firmware) thereon for execution by the computer processor.
[0073] It is noted that various embodiments of the present
invention recited herein can be used separately, combined or
selectively combined for specific applications.
[0074] It is to be understood that the above-described arrangements
are only illustrative of the application of the principles of the
present invention. Numerous modifications and alternative
arrangements may be devised by those skilled in the art without
departing from the scope of the present invention, and the appended
claims are intended to cover such modifications and
arrangements.
* * * * *